Jim Mattis, who recently resigned from his role as secretary of defense, is a something of a legend.

The so-called "Warrior Monk" is famous for quotes like "Be polite, be professional, but have a plan to kill everybody you meet" and "There are some a--holes that just need to be shot."

The following are some of the best quotes from his two-year tenure as the secretary of defense.

Jim Mattis is widely regarded in military circles as one whose reputation borders on the mythological.

Battlefield tactics, quiet-mannered calculations and noteworthy quotes — so many in number they could fill an entire CVS receipt from top to bottom — has elevated the retired Marine general into the pantheon of Marine Corps demigods alongside legends like Chesty Puller, Carlos Hathcock, Dan Daly and Smedley Butler.

And while his time as President Donald Trump's secretary of defense exuded a slightly more toned down "Chaos," as such a position warrants, his tenure in the administration was not without a few memorable statements — "Mattis-isms," as many affectionately refer to them.

With Jan. 1 being Mattis' first day off the defense secretary job, we decided to recap a few of the best Mattis moments that emerged during his tenure.

"YOU'RE NOT SOME P-SSY SITTING ON THE SIDELINES"

Shortly into his tenure as SECDEF, Mattis visited with sailors at Washington state's Naval Base Kitsap-Bangor to personally tell the young men and women in attendance what their military service means.

Always comfortable in his natural service member habitat, Mattis didn't sugarcoat his appreciation.

"That means you're not some p-ssy sitting on the sidelines," he told the sailors, before adding that serving in the military meant none of them would "be laying on a shrink's couch when you're 45 years old, say 'what the hell did I do with my life?'

"Why? Because you served others; you served something bigger than you. ... Some of you aren't old enough to drink a beer, and yet you're the only reason I came back to work in the Department of Defense."

"I KEEP OTHER PEOPLE AWAKE AT NIGHT."

Mattis wasn't exactly fond of getting in front of a camera as defense secretary, a position well documented that many say led to a significantly less transparent system.

One of his only appearances on a network television show, however, did leave viewers with a delectable Mattis morsel, when he appeared on CBS' "Face of the Nation."

Asked by host John Dickerson about what tumultuous world affairs keep the retired general awake at night, Mattis quickly countered, "Nothing. I keep other people awake at night."

"HOLD THE LINE"

Visiting with troops in Afghanistan in 2017, Mattis once again found himself in an environment in which he feels most comfortable: surrounded by fighting men and women.

During a quick pow wow with troops who had quickly assembled — school circle-style — Mattis departed a few encouraging words.

"I know you're far from home, every one of you," he said. "You could all be going to college, you young people, or you could be back on the block — [I'm] grateful. The only way this great big experiment you and I call 'America' is gonna survive is if we got tough hombres like you."

Mattis then went into full-blown general mode when discussing America's enemies on 9/11 — a day he acknowledges some in the audience are too young to remember.

He attributed such acts of terror to an enemy who believed "if he hurt us he could scare us. But we don't freakin' scare," he said. "That's the bottom line. And we'll go out here and we'll fight alongside our friends and allies, and we're gonna keep right on fighting until they're sick of us and leave us alone.

Mattis then praised those encircling him as being role models the rest of the country could look to during a time in which divisiveness was dominating headlines.

"You're a great example for our country right now," he said. "It's got some problems. You know it and I know it. It's got problems that we don't have in the military. You just hold the line, my fine young soldiers, sailors, airmen, Marines. You just hold the line until our country gets back to understanding and respecting each other."

"I'M GOING TO F--KING SEND YOU TO AFGHANISTAN. ARE WE CLEAR?"

Mattis did not favorably receive former Press Secretary Sean Spicer's repeated requests to get the retired Marine Corps general to appear on numerous talk shows, according to an excerpt from Bob Woodward's book, "Fear: Trump in the White House."

According to one passage in the book, an exasperated Mattis, having answered "no" a number of times already, lashed out at Spicer.

"Sean, I've killed people for a living," Mattis reportedly said. "If you call me again, I'm going to f--king send you to Afghanistan. Are we clear?"

"IT'S TO PREVENT WORLD WAR III"

The exchange with Spicer was one of many examples cited in "Fear" that illustrate the communication divide between the White House and the Pentagon.

In one section, Woodward recounts how the president's disconnect from matters of national security prompted Trump to question why the United States was even allocating military resources to the Korean Peninsula at all.

"We're doing this in order to prevent World War III," Mattis answered.

"Mattis was particularly exasperated and alarmed," following the Jan. 19 National Security Council meeting, Woodward wrote, "telling close associates that the president acted like — and had the understanding of — 'a fifth- or sixth-grader.'"

"IF THIS WAS VODKA, IT'D BE A LOT BETTER SPEECH"

Mattis provided a memorable commencement speech for graduates of the Naval War College in June 2018, and as has become his custom, the military's favorite "warrior monk" yielded a few highlight reel quotes that left a lasting impression on those in attendance.

As he navigated his way through the speech, Mattis became noticeably bothered by a scratchy throat.

"That's what you get when you testify too often in front of Congress, by the way," he joked.

Clearing his throat every few seconds, Mattis pressed on.

"In the words of Adm. Chester Nimitz...nothing he encountered in the Pacific during the war was either strange or unexpected, for this campus had prepared him well.

"I'm very confident — thank you very much," he said, halting his speech after an official brought him a bottle of water to remedy the nagging windpipe.

Taking a swig from the bottle, Mattis looked out at the audience and said, straight-faced, "If this was vodka, it'd be a lot better speech," prompting laughter and applause throughout the crowd. "But I'm not supposed to glamorize alcohol anymore," he added. "So you young folks, you ignore what I just said."

"I SALUTE YOU — ONE SECRETARY OF DEFENSE TO ANOTHER"

Maddie Rooney took home a gold medal for Team USA Women's Hockey in the 2018 Winter Olympics. The goalie's nickname — "Secretary of Defense" — and performance caught the eye of Mattis following the gold medal victory.

So much so that Mattis sent a hand-written note to Rooney that read:

"Dear Madam Secretary Maddie, I want to add my congratulations to you and your teammates for your magnificent performance in the gold medal game. You proved yourself in a hard-fought competition and I salute you ― one Secretary of Defense to another! We are all very proud of you. Sincerely, Jim Mattis"